Hydraulically actuated windscreen wiper mechanism



March 31, 1953 H. w. TIEvAsKls 2,633,000

HYDRAULICALLY ACTUATED WINDSCREN WIPER'MECHANISM 2 SHEETS-SHEET i2 H. W.TREVASKIS HYDRAULICALLY ACTUATED WINDSCREEN WIPER MECHANISM 2 5 2 5 J f5f g y/2% A t;

/lU//f//l/ March 3l, 1953 Filed oct. e, 1948 Y piston 3 Patented Mar.31, 1,953

HYDRAULICALLY ACTUATED WINDSCREEN WIPER MECHANISM HenryWilliamTrevaskis, Solihull, England, as-

signer to Dunlop Rubber Company Limited, London, England, a Britishcompany Application October 6, 1948, Serial No. 53,022 In Great BritainNovember 1, 1947 (Cl. Gil-54.5)

4 Claims.

This invention relates to windscreen wipers and more specifically towindscreen wiper apparatus operated by a hydraulic system. f

The object of this invention is to provide a windscreen wiper which isof a simplified nature, which is self bleeding in operation and which islighter in weight and easier to install than previously known apparatus.

According to the invention a hydraulic windscreen wiper system comprisesa windscreen wiper unit and a two-throw pump, the said wiper unitcomprising a housing, a pinion therein mounted cna shaft adapted tocarry a wiper blade, two racks diametrically situated with respect tothe said pinion, two cylinders and single acting pistons, the saidcylinders being adapted to be connected to the said pump and each pistonbeing associated with one of the two said racks, whereby the motion ofone piston in one direction moves the other piston in the oppositedirection, and means for returning to the said pump excess liquid pumpedto the said cylinders.

5 v Fig. 2 is a sectional side elevation of the same wiper unit.

Fig. 3 is a ha1fsectional side elevation of the pump unit associatedwith the wiper unit.

Fig. el is a sectional Yfront elevation of another embodiment of a wiperunit.

Fig. 5 is a halfsectional side elevation of the pump unit associatedwith said wiper unit.

` in one embodiment of the invention an improved hydraulic windscreenwiper apparatus, suitable for iitting to an aircraft consists of a wiperunit, Figs. 1 and 2, and a pump unit, Fig. 3. The wiper unit comprises ahousing I in which two parallel vertical cylinders 2 of equal capacityare disposed side by side, and a single acting is housed within eachcylinder. The lower end of a rack is housed within a socket r5 in theupper end of each piston and the two racks are parallel and extend sideby side with the teeth 6 formed on adjacent sides thereof.

I Disposed between the racks is a pinion I which engages the racks oneither side of its diameter and which is keyed to a shaft rotatablysupported by bearings S in the housing, the wiper ln order that theinvention may be more fully 2 the exterior of the body at its upper endI0b. Two opposed escape ducts II lead from the passage and form ports I2in the walls of the two cylinders adjacent the upper ends of saidcylinders.

Pipe connections I3 and I4 extend from the lower or head end of eachcylinder and another pipe connection I5 extends from the return passage.All three pipe connections are coupled to a pump unit in a manner to beherenafter described. The housing is further provided with two holes I6for connecting said housing to a portion of the aircraft adjacent thewindscreen.

The pump unit Fig. 3 comprises a casing I1 in which is mounted insuitable bearings a crankshaft I8 adapted to be rotated by reductiongearing from an electric motor secured to the casing. The crankshaftreciprocates two pistons I9 retained together by a cradle-like component2B and housed in separate cylinders 2I which are disposed diametricallyopposite each other relative to the crankshaft bearing axis, and whichare secured to the casing. This pump arrangement is herein termed atwo-throw pump.

The pipe I3 from one cylinder in the wiper unit is connected to the headend I3a of a cylinder in the pump unit and the other cylinder of thewiper unit is connected by a similar pipe I6 to the head end Ma of theother cylinder in the pump unit. The pipe I5 connected to the returnpassage in the wiper unit is also connected to the casing of the pumpand inlet passages lead from the pipe connection in the'casing to thepump cylinders and form ports in the walls thereof remote from the headends of saidcylinders.

The operation of the apparatus is as follows. Liquid is introduced inany convenient manner to the four cylinders and associated pipes. Onstarting the electric motor the crankshaft Yis thereby rotated toreciprocate the pump pistons so thatfconsidering one pump cylinder,liquid is expelled therefrom and passes along its respective pipe into awiper unit cylinder whereby the associated piston is traversed to moveits rack and so partially rotate the pinion and wiper arm. Rotation ofthe pinion also moves the other rack so that the two racks move inopposite directions and said other rack traverses its respective pistonto expel liquid from its associated cylinf der and said liquid passesvia the respective pipe units to the appropriate pump cylinder.Continuation of rotation of the crankshaft causes periodic reversals ofthis operation. The volurne of liquid displaced by each pump pistonrduring its pressure stroke is such that during the latter part of saidpressure stroke the associated piston in the wiper unit uncovers theport in its cylinder to allow any excess of fluid to escape from thehydraulic system through a duct in the upper end of the return pass geand into the housing. Liquid can also pass from said cylinder along saidescape duct to the return passage, and through the respective pipe tothe pump unit, where it re-enters the pump cylinders prior to subsequentpressure strokes oi' the pump pis ton. The hydraulic system is thereforeselfbleeding.

A Valve may be located at the upper end of the return passage, saidvalve being normally open to allow oi egress of air :from the passageinto the housing and being automatically closed to prevent loss oiliquid should the wiper unit be inverted.

In another embodiment of this invention Fig. Il a wiper unit comprises ahousing 22 in which is mounted a shaft 23 coupled to a wiper arm.integral with the shaft is a pinion 2i which is engaged atdiaznetrically opposite positions by two racks 2e disposed parallel toeach other with the teeth 2e orzned on adjacent sides thereof. The lowerends of the two racks are associated one with the upper end o one piston'Z7 and the other with the upper end of another piston 28, both pistonsoperating in cylinders 2S formed in the housing, said cylinders being oiequal capacity and disposed parallel and side by side.

One of said pistons is provided with a chamber a centrally1 of its faceand terminating in two smaller holes 22a which extend at an anglethrough the crown of the piston. The inner extremity oi said chamber Siiforms a seating ior a ball 3i which is retained in the chamber by anannular member 52 provided centrally with a hole 33 and its innersurface provided with a plurality of radial slots tl. The wholecornprises a ball valve within the head of the piston.

The cylinder which houses the plain portion, i. e., that piston notprovided with a ball valve, is formed with an annular groove 35 in whichis provided a port it which communicates with the upper end of the othercylinder via a passage way 3l. This groove 35 is positioned in thecylinder' so as to be uncovered by the re spective piston 2t when saidpiston is traversed to the end oi its stroke by fluid pressure. Pipes 38and 39 extend from the lower end of each cylinder and are coupled to apump unit in a manner to be hereinafter described.

The pump unit Fig. associated with said wiper unit comprises a casinglil in which is mounted in suitable bearings a crankshaft Il adapted tobe rotated by reduction gearing from an electric motor secured to thecasing. The crankshaft reciprocates two pistons d2 retained together bya cradle-like component e3 and housed in separate cylinders which aredisposed diametrically opposite each other relative to the crankshaftbearing axis and which are secured to the casing.

` The capacity of one pump cylinder is approximately ten per centgreater than the capacity of the other pump cylinder, which latter has acapacity equal to the capacities of each of the wiper cylinders. Eachpump cylinder' is provided with an annular groove d5 in which isprovided a'jport; 6 and the pcrtscommunicate with a sump All. Thegrooves are positioned in the cylinders so as to be uncovered by therespec= tive pistons when said pistons are at their inner CIJ deadcentre positions. The head end of the smaller capacity pump cylinder hasa pipe connection 38, hereinbefore referred to, to the wiper cylindercontaining the piston provided with the ball valve, while the head endor the larger capacity pump cylinder has a pipe connection 39,hereinbefore referred to, connected to the other wiper cylinder.

The operation of the apparatus is as follows. On starting the electricmotor the crankshaft is thereby rotated to reciprocate the pump pistonsso that, considering the pressure stroke of the piston in the largercapacity pump cylinder, liquid is forced into the one wiper cylinder totraverse the piston and its rack and so partially rotate the pinion andthus oscillate the wiper arm. At the end of the stroke of the piston insaid piston wiper cylinder, the groove and port in said cylinder areuncovered and the excess liquid passes through said port and associatedpassage Way and thus into the other wiper cylinder containing the pistonprovided with the ball valve. At this position or" the pistons the ballwithin the ball valve will be resting on the annular slotted member, andthus the excess liquid may pass through the ball valve and be returnedto the sump in the pump unit by way of the appropriate pipe connection.It is understood that on the return stroke of said pistons the ballwithin the ball valve will be seated by the pressure of the liquid beingforced up from the pump unit.

Rotation of the pinion by one rack causes the other rack to be moved sothat the two racks simultaneously move in opposite directions, saidother rack traversing its respective piston to expel liquid from itsassociated cylinder and said liquid passes via the respective pipe intothe appropriate pump cylinder. Continuation of rotation of thecrankshaft causes the wiper arm and pinion to oscillate about the commonaxis.

By each pressure stroke of the piston in the larger capacity pumpcylinder, the excess liquid is pumped into the wiper cylinder containingthe ball valve so that liquid is continuously circulated through theapparatus from and to the sump. The apparatus is thereforeself-bleeding.

Having described my invention what I ciaim is:

l. A hydraulic windscreen wiper system comprising a two throw pumphaving two cylinders, one cylinder thereoi having a greater swept volumethan the other, and a wiper unit having two cylinders each connected toone of the pump cylinders, the total swept volume oi the wiper cylindersbeing less than that of the pump cylinders, wherein the wiper unitcomprises a housing, a pinion therein mounted on a shaft adapted tocarry a 7wiper blade, two racks diametricallysituated with respect toand engaging with said pinion, a piston in each ci said wiper cylinders,each piston being associated with one of said racks whereby motion ofeach piston in one direction moves the other piston in the otherdirection, one cylinder having an outlet uncovered by its piston at theend of its pressure stroke, said outlet communicating with the othercylinder between its piston and the pinion through a non-return valve inthe other piston.

2. A hydraulic windscreen wiper system comprising a two-throw pumphaving two cylinders, one cylinder thereof having a greater sweptvolurne than the other, and a wiper unit having two cylinders leachconnected to one of the pump cylinders, the swept volume of each wipercylinder being equal to that of the pump cylinder of smaller sweptvolume, wherein the wiper unit comprises a housing, a pinion thereinmounted on a shaft adapted to carry a wiper blade, two racksdiametrically situated with respect to and engaging with said pinion, apiston in each of said wiper cylinders, each piston being associatedwith one of said racks whereby motion of each piston in one directionmoves the other piston in the other direction, and an outlet in onecylinder uncovered by its piston at the end of its pressure stroke, saidoutlet communicating Awith the other cylinder through a non-return valvein the other piston.

3. A hydraulic windscreen wiper system according to claim 2 wherein saidwiper pump comprises a sump and wherein the pump cylinder of greatestswept volume is connected to the Wiper cylinder having the outletuncovered by its piston at the end of its pressure stroke, wherebyexcess fluid delivered to said wiper cylinder from said pump cylinder ofgreater capacity passes through said outlet, through the nonreturn valvein the other Wiper piston and back to said sump.

4. A hydraulic windscreen wiper system according to claim 2 wherein asump supplying said pump cylinders and wherein the non-return valve insaid wiper piston comprises a ball valveclosed during the pressurestroke of said piston and open on its return stroke to allow excessiluid from the other wiper cylinder to flow therethrough and back to thesump.

HENRY WILLIAM TREVASKIS.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 375,674 Greene Dec. 27, 1887677,541 Gruschow July 2, 1901 2,036,100 Richbourg Mar. 31, 19362,181,754 White Nov. 28, 1939 2,190,257 Clench Feb. 13, 1940 2,214,922Ericson Sept. 17, 1940 2,243,385 Levy May 27, 1941 2,389,654 Van derWerff Nov. 27, 1945 2,420,406 Andrews May 13, 1947 2,531,353

Deloghia Nov. 21, 1950

